The present invention relates generally to integrated circuit (IC) packages and more specifically to methods of forming interconnecting contacts for integrated circuit package components.
In the IC packaging industry, there is continuous pressure to reduce the cost of packaging ICs. To accomplish this, a wide variety of package designs and assembly methods have been developed. One of the currently used techniques for producing IC packages is referred to as flip chip packaging. Flip chip packages are typically produced by attaching solder balls or solder columns to input/output terminal pads on the top surface of an integrated circuit die. The solder balls or columns form interconnecting contacts that are used to connect the die to other electrical elements such as a printed circuit board. During the assembly of the flip chip package onto a substrate such as a printed circuit board, the integrated circuit die is flipped upside down such that the solder balls or columns are facing the substrate and is then attached to the substrate. FIG. 1 is a cross sectional view illustrating a typical flip chip package, designated by reference numeral 10, that is attached to a substrate material such as printed circuit board 12.
As shown in FIG. 1, flip chip package 10 includes an integrated circuit die 14 and a plurality of solder ball or solder column interconnecting contacts 16. Interconnecting contacts 16 are attached to associated input/output terminal pads 18 formed on a surface 20 of integrated circuit die 14. Interconnecting contacts 16 are used to electrically connect integrated circuit die 14 to a substrate such as printed circuit board 12.
Because interconnecting contacts 16 are rigid columns or solder balls, these interconnecting contacts form rigid connections between integrated circuit die 14 and printed circuit board 12. These rigid connections are susceptible to cracking or separation due to vibration and/or thermo-mechanical stresses placed on the finished printed circuit board. In order to improve the reliability of the mechanical connection between the flip chip package 10 and the printed circuit board 12, an epoxy material 22 or other such adhesive material is used to underfill flip chip package 10 and adhere package 10 to printed circuit board 12 after the package is assembled onto the printed circuit board. This underfill process is an extra step in the assembly process and adds to the cost of assembling the system using this type of flip chip package.
In order to overcome the above described problem of the rigid contacts and provide an alternative method of forming interconnecting contacts, it is desirable to provide a flexible interconnecting contact for a flip chip package and other interconnection applications. Accordingly, the present invention provides methods of forming flexible interconnecting contacts on integrated circuit package components such as the integrated circuit die of a flip chip package, and eliminates the need for underfill material.